The present invention relates generally to methods and apparatuses for providing electrical and fluid communication to rotating microelectronic workpieces during electrochemical processing.
Semiconductor integrated circuits and other microelectronic devices typically include a substrate or workpiece, such as a silicon wafer, and one or more metal layers disposed on the workpiece. The metal layers are typically used to interconnect components of the integrated circuit. Metal layers may also define devices such as read/write heads, micro electrical-mechanical devices, and other microelectronic structures. The metal layers can be formed from metals such as nickel, tungsten, solder, platinum, and copper. The metal layers can be formed on the workpiece with techniques such as chemical vapor deposition (CVD), physical vapor deposition (PVD), electroplating, and electroless plating.
In one electrochemical plating process, a very thin seed layer of metal is applied to the workpiece using physical or chemical vapor deposition and is deposited to a thickness of approximately 1,000 angstroms. An electrical current is applied to the seed layer while the workpiece is immersed in an electrochemical processing fluid to form a thicker blanket layer on the seed layer. The blanket layer can have a thickness of approximately 6,000 to 15,000 angstroms and can fill trenches, vias and other apertures in the workpiece to provide electrically conductive features within the apertures. After the blanket layer has been electroplated onto the workpiece, excess metal material can be removed (for example, using chemical-mechanical planarization) and subsequent structures can then be disposed on the resulting metal layer.
FIG. 1 is a cross-sectional side elevational view of a conventional apparatus 10 for electroplating a microelectronic workpiece 23. The apparatus 10 includes a cup 12 supplied with electrochemical processing fluid via a supply tube 16. The supply tube 16 also supports a positively charged anode 13. The cup 12 includes sidewalls 17 having an upper edge 18 that defines a free surface 19 of the processing fluid. The processing fluid flows through the supply tube 16, into the cup 12 and over the sidewalls 17 into an overflow vessel 11, as indicated by arrows xe2x80x9cS.xe2x80x9d The fluid can be removed from the bottom of the overflow vessel 11 for disposal or recirculation.
A reactor head 20 supports the microelectronic workpiece 23 relative to the processing fluid in the cup 12 and is movable relative to the cup 12 and the overflow vessel 11 between a closed position (shown in FIG. 1) with the workpiece 23 in contact with the processing fluid, and an open position. The reactor head 20 includes a workpiece support or rotor 21 that supports the microelectronic workpiece 23 in a facedown orientation. The support 21 includes a contact assembly 22 having a plurality of electrical contact points 27 that can be removably coupled to a conductive surface (such as a seed layer) of the microelectronic workpiece 23. A backing plate 4 biases the workpiece 23 into engagement with the contact points 27 and is moveable relative to the workpiece 23 between an engaged position (shown in solid lines in FIG. 1) and a disengaged position (shown in broken lines in FIG. 1). A bellows seal 3 surrounds the backing plate 4. The support 21 is rotatably coupled to the reactor head 20 with a shaft 30 connected to a motor 24. Accordingly, the support 21 and the workpiece 23 can rotate relative to the reactor head 20 and the cup 12 (as indicated by arrows xe2x80x9cRxe2x80x9d) while a negative electrical charge is applied to the electrical contact points 27 to attract conductive ions in the processing fluid to the conductive surface of the workpiece 23.
In one aspect of the conventional arrangement shown in FIG. 1, electrical power is transmitted from the non-rotating reactor head 20 to the rotating microelectronic workpiece 23 via a rotating electrical connection. For example, as shown in FIG. 2, the shaft 30 can include a conductor 31 connected at a lower end to the contact assembly 22 (FIG. 1) and connected at an upper end to a rotary contact 60 that rotates with the shaft 30. The reactor head 20 (FIG. 1) can support a fixed contact 70 that is connected with a cable 34 to a power source (not shown). Accordingly, the shaft 30 and the rotary contact 60 rotate relative to the fixed contact 70 while maintaining electrical contact with the fixed contact 70 and the microelectronic workpiece 23.
In another conventional arrangement, it may be advantageous to purge oxygen from a region proximate to the junction between the microelectronic workpiece 23 (FIG. 1) and the contact assembly 22, for example, to minimize etching of the seed layer and/or reduce the likelihood for oxidizing the seed layer. Accordingly, the apparatus 10 (FIG. 1) can include a purge fluid pathway that provides purge fluid to the support 21 via the shaft 30. In one aspect of this arrangement (shown in FIG. 3), the shaft 30 can include a fluid channel 41 having an entrance port 45 at one end and an exit port 44 at the opposite end. The entrance port 45 extends through the rotary contact 60 and aligns with an axial supply passage 71 extending through the fixed contact 70. The fixed contact 70 also includes a fluid connector 72 for coupling to a source of purge fluid (not shown). Accordingly, the purge fluid can be supplied to the fluid connector 72, through the fixed contact 70, through the rotary contact 60, and through the shaft 30 to the junction region between the microelectronic workpiece 23 and the contact assembly 22.
The invention is directed to apparatuses and methods for transmitting electrical signals and fluids to and/or from a microelectronic workpiece. In one aspect of the invention, the apparatus can include a shaft rotatable about a shaft axis. The shaft can have a first end with a first electrical contact portion toward the first end, a second end opposite the first end, and an internal channel along the shaft axis between the first and second ends. The shaft can further have at least one first hole toward the first end extending radially from the channel to an external surface of the shaft. At least one second hole extends through the shaft from the channel to the external surface of the shaft toward the second end of the shaft. A housing rotatably receives the shaft, and the housing has an aperture coupleable to a fluid source and/or a fluid sink. The housing has a fluid passage positioned adjacent to at least one first hole of the shaft, with the fluid passage in fluid communication with the aperture when the shaft rotates relative to the housing. The housing has a second electrical contact portion engaged with the first electrical contact portion to transmit electrical signals between the first and second electrical contact portions when the shaft rotates relative to the housing.
In a further aspect of the invention, the apparatus can include an inner race fixed relative to the shaft to rotate with the shaft, and an outer race fixed relative to the housing. A first ball-bearing assembly is positioned between the inner race and the housing, and a second ball-bearing assembly is positioned between the inner race and the housing at an axial distance from the first ball-bearing assembly. A first seal is fixed relative to the outer race and is engaged with the inner race proximate to the first ball-bearing assembly, and a second seal is fixed relative to the outer race and engaged with the outer race proximate to the second ball bearing assembly. The inner race, the outer race, and the first and second seals define the fluid passage of the housing.
In still a further aspect of the invention, the housing and the shaft can be included in an apparatus for electrochemically processing a microelectronic workpiece. The apparatus can further include a reactor vessel, a cup disposed in the reactor vessel and having a sidewall to define a level of process fluid within the cup when the process fluid is disposed in the cup, and an anode disposed in the cup and coupleable to a source of electrical potential. A support coupled to the shaft supports the microelectronic workpiece for rotation during electrochemical processing.
The invention is also directed toward a method for transmitting electrical signals and fluids to and/or from a microelectronic workpiece. The method can include transmitting electrical power from a housing to a shaft by engaging a first electrical contact fixed relative to the housing with a second electrical contact fixed relative to the shaft while the shaft rotates relative to the housing about a shaft axis. The method can further include electrically coupling the shaft to the microelectronic workpiece and coupling fluid in an axial channel of the shaft with fluid in the housing. The coupling can be accomplished by aligning, with a fluid passage in the housing, a radial first opening extending from the axial channel to an external surface of the shaft proximate to a first end of the shaft while the shaft rotates relative to the housing and while a second opening proximate to a second end of the shaft is in fluid communication with the surface of the microelectronic workpiece.